The theory of well-off society comes from the ancient and modern ideas of well-off society in China and the Marxist theory of social development stages. The Communist Party of China (CPC) put into prac_x0002_tice the ideal vision of a well-off society, which was developed from the people’s desired state of life to a social model for governing the country. In the course of “one hundred years” of struggle and practice, Chinese Communists have realized the leap from “constructing a moderately prosperous society” to “establishing a moderately prosperous society”, from “building a moderately prosperous society” to “completing the building of a moderately prosperous society”, from “ completing the building of a moderately prosperous society in an all-round way” to “securing a decisive victory in completing the building of a moderately prosperous society”, and have achieved the victory in completing the building of a moderately prosperous society in an all-round way. The realization of building a moderately prosperous society in all respects is of great value. It has enriched the theoretical treasure house of Marxism’s innovation and development in China, laid a solid social foundation for the realization of the Chinese Dream, and contributed China’ s strength to poverty reduction and eradication in the world. It is important to summarize the history and experience of the CPC’s “hundred-year struggle” for a moderately prosperous society in order to start a new practice of building a strong socialist modernization country.